Imprinting apparatus



March 21, 1967 c. PEXTON IMPRINTING APPARATUS s Sheets-Sheet 1 I Filed Dec. 22, 1965 INVENTOR FREDERIC C. PEXTON March 21, 1967 F. c. PEXTON 3,309,97

IMPRINTING APPARATUS Filed Dec. 22, 1965 5 Sheets-Sheet 2 United States Patent 3,309,987 IMPRINTING APPARATUS Frederic C. Pexton, Rochester, Minn., assignor to International Business Machines Corporation, Armonk, N.Y., a corporation of New York Filed Dec. 22, 1965, Ser. No. 515,619 (:iaims. (Cl. 10179) This invention relates to imprinters and, more particularly, to imprinters wherein one or more print wheels are selectively indexable to place print characters into position to transfer an impression to a document in response to printing pressure applied by the print platen.

In imprinter mechanisms an impression is made on a document by squeezing the document between a movable platen and a set of raised characters fixed in a print plane. The platen, often a roller, besides supplying the printing force also supplies the ink, either from an impregnated ribbon contiguous with its surface or from an internally contained reservoir. This permits use of right-reading characters, such as may be carried by a charge plate, drivers license, printwheels, etc., as the impression source.

When indexable print wheels are employed as the impression source, some means are necessary to insure that after each print wheel indexing operation the print surfaces of the selected characters lie precisely in the print plane. If this is not done, printing pressure is not distributed evenly over the character surface and the impression created is, at best, uneven and, at worst, illegible. Often when the surface is badly misaligned with the print plane only a dot or a dash representing the top or bottom edge of the character is printed.

One solution to this problem has been to build into the wheel indexing mechanism the accuracy required to insure the proper character alignment. Another solution has been to provide a separate print wheel alignment mechanism which comes into play after each indexing operation. Both of these solutions are highly undesirable since they add an appreciable amount of cost to the mechanism. Further, the use of compressible type characters, such as are found on the common rubber stamp, is not an answer because such characters are incapable of providing the high reaction forces necessary to generate sharp, clear print impressions. This is particularly true when the document being printed upon includes, as is often the case, multiple carbon transfer layers.

It is therefore an object of the present invention to provide an improved imprinter employing a print wheel bearing print characters the surfaces of which are adapted to be accurately aligned with the print plane in response to pressure from the print platen.

A further object is to provide a print wheel of the type described in the previous object wherein the print characters are formed of substantially incompressible material.

Still a further object is to provide an imprinter wherein the need for accurate print wheel indexing means and/ or for separate print wheel alignment mechanism is eliminated.

Another object is to provide a low cost, self-aligning print wheel for an imprinter.

In accordance with the present invention, an imprinter is provided with one or more indexable print wheels having pivotable character-bearing print members mounted about their peripheries such that printing pressure from the platen causes misaligned characters to be rocked into the print plane to create full, even character impressions. For low cost the print wheels may be manufactured as integral one-piece units.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of Patented Mar. 21, 1967 the invention, as illustrated in the accompanying drawings.

In the drawings:

FIG. 1 is a side elevation view, partially cut away, of a preferred embodiment of the invention wherein a rackgear print wheel indexing mechanism is employed.

FIG. 2 is a partially-sectioned front elevation view of the imprinter of FIG. 1 and shows further details of the indexing mechanism and, in schematic form, depicts details of an automatic roller platen drive mechanism.

FIG. 3 is a diagram depicting the type of undesirable print impressions which may result through use of an imprinter not employing the invention.

FIG. 4 is a front elevation view of a print wheel in accordance with the invention.

FIG. 5 is a sectional view taken along the line 5-5 of FIG. 4.

FIGS. 6a and 6b are schematic diagrams depicting two stages in the operation of the imprinter of the invention.

Referring to FIGS. 1 and 2 a preferred embodiment of an imprinter in accordance with the invention is hereinafter described. A pair of frame members 20 support a pair of stationary shafts 22 and 24, the latter being carried at its right-most end by a frame extension 26. Rotatably mounted about shaft 22 and between the members 20 are four indexable print wheels 12, 14, 16 and 18. These wheels are integrally connected to spur gears 13, 15, 17 and 19, respectively. Appropriate shim means (not shown) may be placed on shaft 22 between the print wheels and frame members to maintain the print wheels in properly spaced positions.

PRINT WHEEL INDEXING MECHANISM Supported on shaft 24 and arranged to cooperate with the gears 13, 15, 17 and 19 are four indexing gears 31, 33, 35 and 37. These gears are rotated through a set concentric drive tubes 32, 34, 36 and 38 by drive gears 41, 43, 45 and 47, respectively. As shown, only the gears 31 and 41, which are interconnected by drive tube 32, bear directly on the supporting shaft 24. Gears 33 and 43, which are interconnected by drive tube 34, bear on the outer surface of tube 32 while gears 35 and 45, which are interconnected by drive tube 36, bear on the outer surface of tube 34 and the gears 37 and 47, which are interconnected by drive tube 38, bear on tube 36.

Drive gears 41, 43, 45 and 47 are rotated by racks 51, 53, 55 and 57, respectively, selected amounts to set desired print characters on the print wheels into printing position beneath a document 10. Each of the racks is actuated in the same manner. As shown for rack 51, a slotted pivot arm 64 pivoted to frame 20 by pin 66 coacts with pin 61 fixed to the right-most end of rack 51. A tension spring 68 biases arm 64 to rotate in a clockwise direction. A plurality of detents 60, one for each print character on a print wheel, control the extent of movement of rack 51 under the bias force of spring 68. The rack is slidably supported by suitable means (not shown). In the embodiment herein shown each print wheel bears ten print characters representative of the numerals 0 through 9. Thus, there are ten detents 60, one for each of the numerals 0 through 9.

In the reset condition the 0 detent is held in an upward position to contact lug 52 on rack 51, preventing rack movement. When the rack is in the position shown, the 0 character of the corresponding print Wheel 12 is set in print position. The detents 60 are controlled in a conventional manner through mechanical linkages or electromagnets from a manually operable selection device such as a keyboard. In selecting the numeral 4, for example, the selection device causes the 4 detent to be moved upwardly into the path of lug 52 While at the same time the 0 detent is withdrawn, allowing the bias of spring ED 68 to rotate arm 64 clockwise which in turn causes rack 51 to be driven to the left until lug 52 strikes the 4 detent. This amount of rack movement rotates drive gear 41 clockwise which, through drive tube 32, causes gear 31 to rotate print wheel 12 a suflicient amount counterclockwise to bring the print character representing the numeral 4 into print position.

To reset the print wheels, reset bail 71 is moved to the position indicated at 71', whereupon arm 64 is rotated counterclockwise against the bias of spring 68 to return rack 51 to its home position. The detent 60, which has been returned to its upward position prior to the reset operation, is resiliently biased so that it moves downwardly as lug 52 passes over it and then snaps back to a detenting position after the lug has passed.

PRINT PLATEN Printing is effected on the top of document by pressure supplied by a platen roller 73. This roller is automatically moved downwardly into an initial printing plane and then drawn to the left through a print stroke by the mechansm shown in FIG. 2. A pair of guide rails 82 having lower guide surfaces 89 are adapted to slide on stationary inclined surfaces 84. The platen roller is rotatably mounted on an axle 75 which is jou-rnaled in a pair of pivotable arms 77. A pair of guide wheels 79 are also rotatably mounted on axle 75 and cooperate with the surfaces 89 to guide the roller 73 in the desired manner. The arms 77 slotably engage a fixed pivot pin 81 and a tension spring 91 connected from pin 81 to a crossbrace member 94 between arms 77 biases the assembly upwardly to keep the wheels 79 in contact with the surface 89 and to maintain guide rails 82 in contact with the surfaces 84.

In the non-printing reset position shown, the guide rails 82 are held to the left against the bias of a compression spring 83 by a detent pin 114 which extends into the path of a crossbrace 83 connected between the rails 82. The arms 77 are held to the right against the bias of a tension spring 97 by a pivotable latch 96 having a finger 93 which hooks behind crossbrace 94. Latch 96 is maintained in the position shown by a tension spring 99 which urges the latch in a counterclockwise direction to hold it against a stationary pin 98.

To actuate the platen roller, a pushbutton 105 is manually depressed to close the circuit to relay coil 107. This rotates pivot member 110 clockwise against the 'bias of tension spring 112, withdrawing detent pin 114 from the path of crossbrace 83. Compression spring 88 then pushes guide rails 82 to the right and downward, the

guide rails following the inclined surface 84. Down- Ward movement of the rails also moves the platen 73 and arms 77 downwardly. When crossbrace 83 contacts stop screw 101 threaded in stationary frame member 103 movement of the rails is arrested. This fixes the lower-most surface of the platen roller in an initial plane, slightly lower than the print plane. As this position is reached, crossbrace 94 is freed from the finger 93 of latch 96 and tension spring 97 pulls the arms 77 and the roller 73 to the left effecting a print stroke.

When the platen contacts the first print wheel 18 the reaction force created urges the platen slightly upwardly into the print plane established by the wheel. This causes the rails 82 to shift slightly up and away from screw 101 against the force of spring 38. Spring 88 acting through the rails 82 thus supplies substantially equal printing pressure to each print wheel, slight variations in the level of the print plane at each wheel being taken up by alterations in the lateral position of the rails 82. The printing pressure causes ink contained internally within the roller 73, which may be constructed of, for example, porous sintered nylon, to be applied to the top surface of document 10, creating an impression thereon of the selected character.

When roller 7 3 has moved to the left a sufiicient amount to generate an impression from each of the print wheels, a crossbrace 92 connected between the arms 77 strikes a stop pad 87 supported on a crossbrace connected between the guide rails 82. The force of this impact is sufiicient to move the guide rails 82 upwardly and to the left against the bias of spring 88, withdrawing the guide surfaces 39 and platen 73 away from the surface of the document. When the rails 82 have moved far enough to the left, the bias of spring 112 pivots arm counterclockwise to re-insert detent pin 114 into its blocking position, holding the guide rails 82 in their left-most position. Thereafter, suitable reset means (not shown) are employed to pivot the arms 77 counterclockwise until crossbrace 94 re-engages finger 93 of latch 96. It is to be noted that during this resetting movement of platen roller 73 printing is not effected since guide surfaces 89 are in their uppermost position and the lower surface of roller 73 maintained out of contact with the document.

PRINT WHEELS Referring now to FIGS. 4 and 5, the novel construction of the print wheels is hereinafter described. The print wheel itself is preferably a one piece unit integrally manufactured through a molding or machining operation. The wheel comprises three basic portions: a hub member 124, a plurality of flexible support members 126 extending radially outwardly from the hub and a print member 128 mounted on each support member 126. Each print member carries on its outer surface a raised character representation such as that of a numeral, as shown. A side- Wardly extending collar may be provided on the hub 124 to enable attachment of spur gear 19 by means of a pair of rivets 122 or other suitable fastening means.

As has been previously generally described, the essence of the present invention stems from the ability of each of the print members 128 to pivot or tilt on their respective support members 126 in response to printing pressure from the print platen, thus avoiding the type of adverse print results depicted in FIG. 3. The amount of force required to accomplish this pivoting action is dependent upon the thickness of the members 126 and upon the material of which those members are constructed. The type of material is important from another standpoint in that the pivoting action of the print members must not be accompanied by any material amount of radial compression of the support members since such compression would permit the print member to move radially inwardly in response to printing pressure, thus reducing the reaction force generated at the printing surface and materially degrading the quality of the printed impression. For this same reason the raised character representations 129 carried on the print members must also be substantially incompressible.

While it .is recognized that the specific materials and dimensions chosen for the print wheel will vary with different applications, it has been found that suitable results are obtained by forming the entire print Wheel, including the raised character representations 129, integrally, either through a molding process or a machining operation, from either a polycarbonate resin such as is marketed by General Electric Company under the trademark l/exan or from an acetal resin such as is marketed by E. I. du Pont de Nemours and Company under the trademark Delrin. Both these materials are available with tensile moduli (also known as the modulus of elasticity in tension) within a range from 200,000 to 500,000 p.s.i. Moduli within this range provide the desired flexibility and incompressibility in the members 126. Exemplary of suitable dimensions for the print wheel are an overall diameter of substantially 1.3 inches, in width of substantially .25 inch, a support member width (dimension A) of .032 inch and a support member height (dimension B) of .125 inch. It is to be understood that these various dimensions and materials are exemplary only and might well be altered for various printing applications without departing from the scope of the in. vention.

OPERATION Referring now to FIGS. 1, 2, 6a and 6b, the operation of the imprinter of the invention is hereinafter described. After a print Wheel indexing operation has been performed to selected desired print characters, pushbutton 105 is depressed to initiate the print cycle. This withdraws detent pin 145 from its blocking position and permits compression spring 88 to move guide rails 82 to the right and downwardly until stop screw 101 is met. This places the lower surface of the platen roller in its starting plane and frees the arms 77 from the influence of latch 96. Platen roller 73 thus begins moving to the left under the influence of spring 97 with its lower surface tangential to the starting plane. As shown in FIG. 6a, a print wheel has been inaccurately indexed and as the roller platen 73 approaches it (from the rear) the left edge L of the surface of the selected print character is above the print plane while the right edge R is below it. When the platen roller contacts the print character as shown in FIG. 6b, the print member on which the character is contained is forced to pivot counterclockwise upon its flexible support member 126 until the surface of the character is in exact alignment with the print plane established by the lower surface of the platen. Thus, as the platen traverses the surface of the character an extremely even, highly legible, character impression is generated on the upper surface of the document 10. As the platen 73 continues its print stroke a similar action occurs at each misaligned print character.

Thus it is seen that with the present invention accurate alignment is achieved between the surfaces of the print characters and the surface of the platen without requiring separate print wheel alignment devices such as rack or gear alignment bails, print wheel gear detents, etc., and that the tolerances required of the gear teeth on the set-up racks such as rack 51 and on the intermediate drive gears need not be close, meaning that a relatively great amount of backlash or play may be permitted to exist between the gear-teeth without sacrificing print quality.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be madetherein without departing from the spirit and scope of the invention.

I claim:

1. In a printing apparatus, the combination comprising:

a print platen;

means for driving said platen to apply printing pressure to the surface of a document lying in a print plane; and

a rotatable print wheel having a plurality of characterbearing print members pivotally mounted about its periphery, each of said members being constrained so as to pivot in an are which is radially fixed with respect to the center of rotation of said wheel, said Wheel being selectively indexable to place the surface of a character into substantialy alignment with said print plane on the opposite side of said document from said platen, said print members being resiliently biased to an initial position whereby said platen, in applying said printing pressure, urges the surface of said substantially aligned character to pivot into exact alignment with said plane.

2. The printing apparatus set forth in claim 1, wheresaid platen comprises a roller; and

said driving means comprises means for moving the axis of said roller along a predetermined path to maintain the surface of said roller tangential to said 5 print plane.

3. The printing apparatus set forth in claim 2, wherein: the axis of said roller is perpendicular to the axis of rotation of said print wheel; and

said driving means is constructed and arranged to move sa1d roller in a direction which is parallel to said axis of rotation of said print wheel.

4. A print wheel comprising: a rotatable hub;

a plurality of print members each bearing a raised character representation; and

resilient support members pivotally connecting said print members to said hub such that each said print member is constrained to pivot in an arc which is fixed with respect to said hub and which lies in a plane which is substantially perpendicular to the axis of rotation of said hub. 5. The print wheel set forth in claim 4 wherein:

each said support member comprises a flexible, substantially incompressible column radially extending from said hub.

6. The print wheel set forth in claim 5 wherein:

each said column supports one print member and is joined to said print member at substantially the midpoint of the latter.

7. The print wheel set forth in claim 6 wherein:

each said raised character representation is formed of a substantially incompressible material. 8. The print wheel set forth in claim 7 wherein:

terial. 9. The print wheel set forth in claim 8 wherein:

500,000 p.s.i. 10. The print wheel set forth in claim 8 wherein:

said material is an acetal resin having a tensile modulus within a range from 200,000 p.s.i. to 500,000 p.s.i.

References Cited by the Examiner UNITED STATES PATENTS References Cited by the Applicant UNITED STATES PATENTS 7/ 1914 Snyder.

5/1959 Terry. 7/ 1964 Brown et a1.

Dietrich Brown et a1 said hub, said print members, said support columns and said raised character representations are integrally formed from one piece of the same masaid material is a polycarbonate resin having a tensile modulus within a range from 200,000 p.s.i. to

Snyder 101406 Adams 19753 197-1 Terry 101--93 Leeds 101395 X Maul 101269 X 10199 Beaver 101376 X 

1. IN A PRINTING APPARATUS, THE COMBINATION COMPRISING: A PRINT PLATEN; MEANS FOR DRIVING SAID PLATEN TO APPLY PRINTING PRESSURE TO THE SURFACE OF A DOCUMENT LYING IN A PRINT PLANE; AND A ROTATABLE PRINT WHEEL HAVING A PLURALITY OF CHARACTERBEARING PRINT MEMBERS PIVOTALLY MOUNTED ABOUT ITS PERIPHERY, EACH OF SAID MEMBERS BEING CONSTRAINED SO AS TO PIVOT IN AN ARC WHICH IS RADIALLY FIXED WITH RESPECT TO THE CENTER OF ROTATION OF SAID WHEEL, SAID WHEEL BEING SELECTIVELY INDEXABLE TO PLACE THE SURFACE OF A CHARACTER INTO SUBSTANTIALY ALIGNMENT WITH SAID PRINT PLANE ON THE OPPOSITE SIDE OF SAID DOCUMENT FROM SAID PLATEN, SAID PRINT MEMBERS BEING RESILIENTLY BIASED TO AN INITIAL POSITION WHEREBY SAID PLATEN, IN APPLYING SAID PRINTING PRESSURE, URGES THE SURFACE OF SAID SUBSTANTIALLY ALIGNED CHARACTER TO PIVOT INTO EXACT ALIGNMENT WITH SAID PLANE. 